Posted by
Geoffrey Mackenzie-Kennedy-2 on
May 28, 2005; 11:49am
URL: http://elecraft.85.s1.nabble.com/K2-XTALS-tp378841p378842.html
Morning Colin,
My K2 is #3255 and the KSB2 Build is Revision C-3. The envelope that
contained the KSB2 crystals is marked 3.7 (as was the envelope containing
the K2's IF filter crystals), and the KSB2 crystals are marked 4.9136. I
have not made any modifications From 'swept' measurements the KSB2's
filter -6db bandwidth is 2.1 kHz approx if I remember correctly Please note
that this is not a 'noise loaded' measurement, e.g. Spectrogram. The exact
figure is in my notebook which is packed away due to an invasion of
plumbers, carpenters and others - sorry about that.
Using this data and the measured audio response, mic connector to and
including the modulator, to set the carrier oscillator frequencies (BFO),
the BFO is no more than 200 Hz away from the frequencies suggested in the
KSB2 manual. With a Heil ProSet Plus and no audio mods, full specd PEP is
obtained and unsolicited audio reports are complimentary.
My personal opinion is that the 2.1 kHz bandwidth is satisfactory with the
K2, for ragchewing and DXing. Because the same intermediate sized crystal
ladder filter is used for both USB and LSB, increasing the bandwidth could
result in problems with unwanted sideband suppression when the BFO is on the
low frequency skirt of the filter. This assumes that the filter is properly
designed and terminated. It is possible to fiddle things to steepen the LF
skirt, but usually at the cost of increased ripple in the passband.
73,
Geoff
GM4ESD
----- Original Message -----
From: "m1bnw" <
[hidden email]>
To: <
[hidden email]>
Sent: Friday, May 27, 2005 7:18 PM
Subject: [Elecraft] K2 XTALS
I am buiding a K2 sn 004149 from an earlier non built K2 sn 000571 up to rev
'B' on the new 'B' pc boards.
I also have an early KSB2 SSB unit.
All the above has the original XTALS for the CW filter and SSB unit.ie
4.195MHz -20.
I have read lots of comments on the audio quality because of the tight band
pass of the original SSB unit.
I know that Elecraft have produced some modifications in the form of 14 new
XTALs and a capacitor upgrade kit.
Does anyone have experience of these mods ?
Is there a basic capacitor upgrade that one can do first of all?
Or is changing all the XTALs and adding new capacitors the best solution?
Or is the original configuration ok?
Regards Colin M1BNW
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